Plastic polymer compositions



Patented July 8, 1941 UNITED STATES PATENT j omcr PLASTIC POLYMERCOMPOSITIONS Harold W. Fisher, Cranford, N. J., asslgnor to Standard OilDevelopment Company, a corporation of Delaware No Drawing. ApplicationJune 22, 19s

. Serlal No. 149,693

3 Claims. (Cl. 260-41) molekulare Verbindungen.

According" to the present invention, it has been found that a tremendousimprovement in the properties of such polymers is effected byincorporating therewith a substantial amount of carbon black.Theinvention may be illustrated by a composition consisting essentiallyof 90% 150- butylene polymer having an average molecular weight of about80,000, and about 10% of finelydivided carbon black. The invention willbe described more in detail further on.

Although the preparation of the polymer itself is not per se part of thepresent invention,

it will be described briefly in order that the invention may be betterunderstood. The process will bedescribed as particularly applied to thepolymerization of isobutylene, although other olefins having a. similarchemical structure and capable of polymerizing to a very high molecularweight linear type polymer with short alkyl side chains may also beused. Isobutylene is polymerized in the presence of a volatile inorganichalide, particularly boron fluoride, at temperatures below 10 C,, suchas at about -50 C. or

even as low as l00 C. The reaction is preferably carried outin thepresence of a suitable solvent for the isobutylene, such as some of theliquefied normally gaseous-hydrocarbons, for instance, propane;ethylene, etc. The resulting polymer which is recovered afterevaporation of V the solvent by release of pressure and warming to roomtemperature and then washing with water or dilute caustic soda orotherwise purified to remove any residual catalyst, is a substantiallycolorless, plastic solid having an average molecular weight range fromabout 3,000 up to 500,000

or so,,although the conditions are preferably regulated so as to producea polymer having an average molecular weight of-about 15,000 asrepresenting the lower range, or about 80,000 as a medium molecularweight, or about 200,000 as representing the extremely high molecularweight polymers. The product should preferably contain less than 0.1%and preferably not more than .01% of inorganic salt impurity. It isparticularly important in preparing the extremely high terials should befree from sulfur compounds and other substances which act as poisons tothe polymerization of isobutylene.

If desired, the polymerized product may be separated into fractions fordifferent molecular weights, either by. selective extraction or solutionand precipitation using solvents, such as ethane, propane, naphtha,benzene, acetone-benzine, etc.,

at the proper temperature to make the desired I separation. In this waythe polymers having any particular desired molecular weight range may beseparated from those having higher or lower molecular weights.

Although it is preferred to use boron fluoride as the catalust, one mayalso use dry aluminum chloride, phosphorus tri-fluoride,phosphoruspenta-fluoride, etc., or other active inorganic halides,although these may not give as good results as the boron fluoride.

The polymer having a molecular weight in the lower range, 1. e. fromabout 3,000 to 25,000 has somewhat of a tendency toward what is calledcold flow; although it does not soften appreciably on heating as doparaflln wax, bituminous materials and otherwaxy or plastic substances,yet upon standing for any substantial length 'of time it will tend toflow" very slowly but perceptibly. This low molecular weight product isalso very tacky. On the other hand the polymers having substantiallyhigher molecular weights, such as 80,000 to 100,000 or 200,000 or more,have relatively little tendency toward cold flow and are dry and nottacky to the touch. They also possess considerable snap.

These polymers are all substantially saturated in respect to hydrogenbecause the only double bond present in the molecule is relativelyinsigniflcant in view of all of the'rest of the molecule which isentirely saturated and free from double bonds. Therefore, although thesepolymers, especially those of high-molecular weight, are somewhatrubbery in physical nature, yet they are not very amenable to theordinary hardening byvulcanization with sulfur as can be appliedmolecular weight polymer that the starting manomenon.

most remarkable fact, however, is that by sc' doing the durability ofthe polymers is also improved due to the increased resistance of thecomposition against light or ultra-violet rays having any tendency todepolymerize the polymer. Another object of the invention is to 11mprove the physical properties mentioned without at the same timereducing the resistance of the polymer to chemical action.

In carrying out the present invention, carbon black is mixed with thehydrocarbon either before, during, or after polymerization and if doneafter the evaporation of the solvent (used in the polymerizationprocess) the mixing is preferably accomplished by a kneading machine,although a' pair of steel rollers, such as those used in a typicalrubber mill, may also be used. Thecarbon black to be used is preferablylamp black because it can be obtained in a state of very finesubdivision, although undersome circumstances coarser grades may beused.

The amount of carbon black to be used may vary undera fairly wide'ran'gedepending largely upon the molecular weight of the polymer and thefineness ,of the carbon black used, as well as the .particular use towhich the composition is to be applied. However, in general, thecomblack if the product is to be used in sheet form or is to be extrudedor otherwise manipulated under conditions requiring substantialplasticity. Under these circumstances the amount of carbon black shouldpreferably be between -30% using the lower range, 1. e. about 5-15% or20% when the carbon black is extremely fine and the larger range, 1.e.'15-30% when the carbon black is very coarse. When the composition isto be position may contain about 1-50% of carbon subjected to moldingunder pressure for the production of substantially rigid articles afmuchlarger amount of carbon black should be used. usually between theapproximate limits of 30- 80% or more, although generally about -60%will be sufficient. The larger the amount of carbon black used the morepressure will be required for the molding. This pressure may range, forinstance, from 100 to 10,000 pounds per square inch.

It is interesting and in fact very surprising that the isobutylenepolymer will tolerate considerably more carbon black than ordinaryrubber. Although the exact reasons for this phenomenon are not wellunderstood, it is believed due to the higher wetting power of thepolymer.

1 addition to the carbon black 'it' may also be desirable .under somecircumstances to add small amounts of other materials, for instance,

plasticizers, such as waxes, oils, etc. or hardening agents, such asresins, pigments, rubber, etc. Improved compositions prepared asdescribed above are particularly useful for preparing extrudablearticles, such as. flexible hose or tubing or sheet material which maybeused, for instance, as table covering, floor matting,-etc., or cut outin the shape of gaskets or molded products, such as bottle stoppers,tiles, etc.

The following examples are given for the sake of illustration withoutintention of limiting the invention specifically thereto:

Examplel I 5% of lamp black was kneaded into 95% of isobutylene polymerhaving a molecular weight of about 80,000. The composition was muchbetter suited to calendering and sheeting than the, polymer without thelamp black. v

I Example 2,

The test in Experiment 1 was repeated using 10% of lamp black and thencalendering was found to be still better and the resulting product wasconsiderabl tougher.

Example 3 30% of lamp black was mixed with 70% of the same polymer usedin Example 1' and the resulting product was also suitable forcalendering and sheeting and was still quite elastic" and tough.

' Example4 of carbon black was mixed with 40% of isobutylene polymer ofabout 15,000 molecular weight and the mixture was compressed and moldedinto various shapes such as bottle stoppers, tiles, etc.

Example 5 20% of carbon black was mixed with 40% of isobutylene polymerhaving a molecular weight of about 80,000 and 40% of paraiiin wax havinga melting point of about 120 F. The mixing and resulting sheeting wereeffected at about 212 F.

- Example 6 1 30% of carbon black was mixed with 50% of isobutylenepolymer having a molecular weight of about 80,000 and20% of. ester gum(a normally hard brittle glyc'erol ester of rosin) and the resuitingmixture sired shapes. s I

It is notintended that the invention be limited by any or the specificexamples given herein above or by any theories of the operation of theinvention, but only by the appended claims in which it is' intended toclaiigiail novelty inherent in the invention as art permits.

I claim:

bro y as the prior' 1. A shaped substantially rigid article ofmanufacture composed of isobutylene polymers having an average molecularweight "above about 15,000, and a substantial amount of carbon blacksumcient to retard softening of the polymer when exposed to lightand tomake the article retain its shape. 2. A .sheeted article made of thecomposition according to claim 1 and containing about 5. to 50% ofcarbon black.

3. A molded articlelmade of the composition according to claim 1 andcontaining about 30 to of carbon black.

" HAROLD W. FISHER.

was molded into articles of de-

